1. Field of the Invention
The present invention generally relates to contact lenses. More particularly, the present invention relates to methods for improving the hydrophilicity of contact lenses, and contact lenses having the same.
2. Description of the Related Art
Vision correction is on the verge of a revolution. New technologies to measure the aberrations or distortions in the optics of the eye will soon be available to the public. These new wavefront measurement techniques such as Shack-Hartmann wavefront sensing or Talbot Interferometry can precisely measure the eye's aberrations so that vision may be corrected up to 20/10. Wavefront sensing is the method for rapidly, and very accurately, assessing the aberrations in an individual's eye to create a customized prescription for correction.
However, once the eye's aberrations have been measured, either by conventional methods or by wavefront sensing, these measurements must then be transferred into a vision correction system, such as eye surgery, spectacles, or contact lenses. Recent advances in laser refractive surgery techniques such as LASIK and photorefractive keratectomy, as well as improvements in spectacle lens manufacturing now enable the creation of highly accurate corrective prescriptions for individuals.
However, this is not the case with contact lenses. Popular soft contact lenses cannot achieve the same result as spectacles or laser refractive surgery because of dimensional variations in fabrication. Rigid gas permeable (RGP) contact lenses, which may provide the platform to achieve the results of spectacles, are not as comfortable as soft contacts and lack the necessary positional stability on the eye.
Hybrid hard-soft contact lenses comprising a high Dk hard center portion and a relatively soft outer skirt have been developed to provide a platform for a corrective prescription and also provide the comfort of soft contact lenses.
One characteristic of contact lenses, both RGP and hybrid contact lenses, that is important to their level of comfort during use is the gas permeability of the contact lens material. Contact lens manufactures have usually attempted to increase gas permeability by adding silicon, styrene, fluorine, or a combination of these moieties to the contact lens material. However, these materials are hydrophobic and thus tend to have a high contact angle, and reduced or limited wettability of the lens. Wettability of the lens surface is important because it allows tears to fill the lens-corneal interspace. Further, wettability facilitates a uniform pre-lens tear film, thereby supporting the integrity of the optical characteristic of the front surface of the lens including subtle aberration structures manufactured thereon.
Existing ways of improving the wettability of contact lens surfaces include the periodical soaking of the contact lens in a conditioning cleaning solution and plasma charging of contact lens surfaces. However, such methods only temporarily improve the wettability of a contact lens. For example, plasma charging of contact lens surfaces generally provides improved wettability for 30 to 40 days, after which the material returns to its hydrophobic state.
With respect to conditioning cleaning solutions, a user must periodically remove the contact lenses and soak them in the solution for a period of time before wearing the lenses. Existing solutions only temporarily increase the wettability of the lens. However, a user must continue to periodically soak the contact lenses in the solution, which prevents the user from wearing the contact lenses for an extended period of time. This approach is inefficient since users may sometimes forget to clean their contact lenses. If the lenses are not periodically soaked, the user may experience increased discomfort from extended wear of the contact lenses.
Accordingly, there is a need for a contact lens with improved hydrophilicity and increased wettability that is long lasting, allowing for the continuous comfort wear of contact lenses.